1. Field of the Invention
This invention relates to a system for transferring antenna control data to a control circuit for a phase shifter in each of the antenna elements.
2. Description of the Prior Art
FIG. 1 is a schematic representation of the arrangement of a conventional system for transferring antenna control data, which comprises, as shown antenna elements (apertures) 1a-1d for transmitting or receiving electromagnetic waves, duplexers 2a-2d for transmitting the antenna elements for alternate use for transmitting and receiving electromagnetic waves to and from the antenna elements 1a-1d, respectively, a duplexer control signal line 3 for feeding a duplexing signal to the duplexers 2a-2d, and phase shifters 4a-4d for shifting the phase of the electromagnetic waves to be transmitted or received by the antenna elements 1a-1d, respectively. The system shown in FIG. 1 further includes phase shifter control circuits 5a-5d for controlling the amount of phase shift of the electromagnetic waves given by the phase shifters 4a-4d, respectively, a data line 14 for transferring data for controlling the phase shifters 4a-4d to each of the phase shifter control circuits 5a-5d, a clock line 15 for carrying a clock which serves as a trigger signal for each of the circuits 5a-5d when it performs processing operations such as latching the data transmitted from the data line 14, a reset line 16 for transferring a reset signal for resetting each of the circuits 5a-5d, X-enable lines 29a and 29b commonly connected to such ones of the circuits 5a-5d as positioned in the same X-row, and Y-enable lines 30a-30b commonly connected to such ones of the circuits 5a-5d as positioned in the same Y-row.
FIG. 2 is a schematic representation of the arrangement of the exemplary circuit 5 of the phase shifter control circuits 5a-5d of the antenna control data transfer system shown in FIG. 1. The circuit 5 comprises a phase data holding circuit 6 for holding the phase data or the amount of phase shift of the electromagnetic waves given by the associated phase shifter 4, a signal processing circuit 7 for performing signal processing operation in accordance with the data from the data line 14, a coordinate holding circuit 9 for holding the coordinates of associated ones of the antenna elements 1a-1d, a phase factor holding circuit 10 for holding a phase factor to be used when the signal processing circuit 7 computes the amount of phase shift of the electromagnetic waves in accordance with the data from the data line 14, and a correction data holding circuit 11 for holding a correction data for compensating the computed value for error caused by variations in electrical length of the transmission of the electromagnetic waves to the respective antenna elements, etc.
In operation, the phase of an electromagnetic wave transmitted or received by each of antenna elements 1a-1d is set according to the following Equation (1) so that the whole set of antenna elements 1a-1d may transmit or receive a beam of electromagnetic waves in a desired direction: EQU .phi..sub.n =k.times.(P.sub.n .multidot.D)+C.sub.n ( 1)
where
n=a, b, c, d; PA0 .phi.n is the phase data or the amount of phase shift of an electromagnetic wave transmitted or received by the antenna element 1n; PA0 P.sub.n is the position vector of the antenna element 1n, the components of P.sub.n representing the coordinates of the antenna element 1n; PA0 and D is a unit direction vector in a desired beam direction.
Thus, P.sub.n .multidot.D is the inner product of two vectors P.sub.n and D. Further, k is a phase factor depending upon the electromagnetic wave frequency; and C.sub.n is a correction data for compensating the computed value for the error caused by variation in electrical length of the transmission of the electromagnetic waves to the antenna element 1n, etc.
In order to set the beam of electromagnetic waves in a desired direction, the data of the respective components of the unit direction vector D in the desired direction is transferred through the data line 14 to each of the phase shifter control circuits 5a-5d. When each of the circuits 5a-5d has received that data, the signal processing circuit 7 therein computes the phase data or the amount of phase shift of the electromagnetic waves in accordance with Equation (1) using the received respective components of the unit direction vector D in the desired beam direction, the coordinates of each of the antenna elements 1a-1d, i.e., the respective components of the position vector P.sub.n of each of the antenna elements, fetched from the associated coordinate holding circuit 9, the phase factor k fetched from the associated phase factor holding circuit 10 and the correction data fetched from the associated correction data holding circuit 11 for correcting the error in the computed value caused by variation in electrical length of the transmission of the electromagnetic waves to each of the antenna elements 1a-1d, and then feed the derived phase data to the phase data holding circuit 6. The phase data holding circuit 6 temporarily stores the fed phase data and also supplies it to an associated one of the phase shifters 4a-4d. The phase shifters 4a-4d operates in response to the phase data to shift the phase of the electromagnetic waves to be transmitted or received by the respective antenna elements 1a-1d.
In this manner, when the components of the unit direction vector D of the beam in the desired direction are transferred as data to each of the phase shifter control circuits 5a-5d, the phase data or the amount of phase shift of the electromagnetic waves to be transmitted or received by the respective antenna elements 1a-1d is computed and the computed phase data is transferred through the phase data holding circuit 5 to the associated phase shifter 4, so that the phase of the electromagnetic waves transmitted or received by each of the antenna elements 1a-1d is varied in accordance with Equation (1) by each of the phase shifters 4a-4d associated with each of the antenna elements. Thus, the beam of electromagnetic waves transmitted or received by the whole antenna elements 1a-1d is directed in the desired direction.
The data inputted into the respective phase shifter control circuits 5a-5d is accepted only when an X-enable signal and a Y-enable signal are simultaneously supplied to both the X-enable and Y-enable lines 29a, 29b and 30a, 30b, respectively, connected to the respective phase shifter control circuits 5a-5d. In the event of transfer of data which is common to all of the phase shifter control circuits, such as each of the components of the unit direction vector D in the desired direction, the transfer of such data may be achieved while the X-enable signal are supplied to all of the X-enable lines 29a, 29b and the Y-enable signal also to all of the Y-enable lines 30a, 30b. In contrast, in the case that individual data is transferred to the specified phase shifter control circuits 5a-5d, that is, in such an event that the coordinates of the respective antenna elements 1a-1d or the correction data corresponding thereto are held in their coordinate holding circuit 9 or correction data holding circuit 11 in the initial condition, for example when it is preferable for data to be transferred only to the phase shifter control circuit 5a, X-enable signal is supplied only to the X-enable line 29a and Y-enable signal also only to the Y-enable line 30a. Thus, the data may be transferred in such a condition that the X-enable and Y-enable signals have only been supplied to X-enable and Y-enable lines 29a, 29b and 30a, 30b connected to phase shifter control circuits to which the data is transferred.
As described above, in the prior art system for transferring antenna control data, when the data is transferred to each of the phase shifter control circuits 5a-5d, the X-enable and Y-enable lines 29a, 29b and 30a, 30b are used and thus the number of the X-enable and Y-enable lines must be increased as the number of the antenna elements increases.
Furthermore, since the data line 14 is also commonly connected to the phase shifter control circuits 5a-5d, if the number of the antenna elements 1a-1d exceeds the maximum connections to a data supply circuit (not shown) outside the antenna control data transfer system, it will then be necessary to increase the number of the data lines 14. This is also true of the X-enable and Y-enable lines 29a, 29b and 30a, 30b. Therefore, there were drawbacks that as the number of the antenna elements increase the number of the X-enable and Y-enable lines 29a, 29b and 30a, 30b and the data lines 14 is increased, and correspondingly the number of the external connections of the system is increased.